A waste stone powder-steel slag multi-element solid waste-based cementitious material and a preparation method thereof

Abstract

The present application relates to the technical field of building materials, in particular to a kind of waste stone powder-steel slag multi-element solid waste-based cementitious material and its preparation method.The present application uses waste stone powder, steel slag and mineral powder mixture, desulfurization gypsum as raw material, and further optimizes component proportion and water-binder ratio.The present application stimulates the activity of steel slag and mineral powder by the sulfate of desulfurization gypsum, generates ettringite and C-S-H cementitious;And stone powder does not participate in hydration reaction in cementitious material, only plays "inert filling function".The present application optimizes the pore structure of cementitious material by stone powder filling effect, compared with conventional technology without adding chemical activator.The cementitious material prepared by the present application has excellent mechanical properties and good stability, and is a truly green and low-carbon "cement-free full solid waste system".

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a waste stone powder-steel slag multi-element solid waste-based cementitious material and its preparation method. Background Technology

[0002] Steel slag is one of the largest solid wastes emitted by the steel industry. It contains active minerals such as C2S and C3S, possesses a certain hydration capacity, and can be used to prepare cementitious materials. Meanwhile, a large amount of waste stone powder is generated during stone processing. This powder is fine-grained, readily available, and inexpensive, but its utilization rate is currently low, and it is mostly disposed of through stockpiling, causing land occupation and environmental pollution.

[0003] Existing technologies have researched the preparation of composite cementitious materials by compounding steel slag with solid wastes such as mineral powder and desulfurized gypsum. Chinese patent application number CN202110481301.0 discloses a building material prepared from waste stone powder, comprising the following raw materials in parts by weight: 40-80 parts waste stone powder, 10-40 parts mineral powder, 5-10 parts steel slag, 5-10 parts desulfurized gypsum, and 1-5 parts admixtures; the admixtures are alkaline activators, aluminates, and water-reducing agents. This invention relies heavily on multiple admixtures, and the material has relatively low strength, which limits its application to some extent. Addressing the problem of unclear understanding of the role mechanism of waste stone powder in multi-component solid waste systems and the lack of systematic mix design methods in existing technologies, developing a multi-component solid waste-based cementitious material that balances mechanical properties and stability, and maximizes the utilization of waste stone powder, has significant engineering and environmental value. Summary of the Invention

[0004] The purpose of this invention is to provide a waste stone powder-steel slag multi-element solid waste-based cementitious material and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A waste stone powder-steel slag multi-element solid waste-based cementitious material, by weight, comprises: 8.8~18.4 parts waste stone powder, 70.4~92 parts a mixture of steel slag and mineral powder, and 8~12 parts desulfurized gypsum, with a water-cement ratio of 0.4~0.5.

[0007] Furthermore, in the mixture of steel slag and mineral powder, the mass ratio of steel slag to mineral powder is 1:2 to 1:4.

[0008] Furthermore, the waste stone powder has an average particle size of 5 μm, and its main component is CaO with a content of ≥97 wt.%.

[0009] Furthermore, the steel slag has a fineness of 100~200 mesh and a 28-day activity index ≥95%.

[0010] Furthermore, the ore powder is S95 grade granulated blast furnace slag powder with a specific surface area ≥442m². 2 / kg.

[0011] A method for preparing a waste stone powder-steel slag multi-element solid waste-based cementitious material includes the following steps:

[0012] Step 1: Weigh the waste stone powder, steel slag, mineral powder and desulfurization gypsum according to the ratio, pour them into the mixing pot and stir slowly for 120 seconds to make them fully mixed.

[0013] Step 2: Weigh out water according to the water-cement ratio, add it to the mixing pot, stir slowly for 120 seconds, stop for 15 seconds, and then stir quickly for 120 seconds to obtain the slurry;

[0014] Step 3: Pour the slurry into the mold and vibrate it to form the shape. After curing at room temperature for 24 hours, move it to a standard curing room (temperature 20±2℃, relative humidity ≥95%) for curing until the specified age.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0016] (1) Innovation in synergistic hydration mechanism: Existing technologies typically focus on activation methods to make stone powder "play a role," while this application clarifies for the first time the "inert filling function" of stone powder: utilizing its characteristic of not participating in the hydration reaction, the water absorption coefficient and shrinkage rate of the material are systematically reduced. This invention uses "waste stone powder + steel slag + mineral powder" as the main body, making full use of its "inert filling function" to exert the micro-aggregate filling effect and optimize the pore structure. Therefore, this invention does not require any external chemical activators, but only uses the sulfate activation of desulfurized gypsum to activate the activity of steel slag and mineral powder, generating ettringite (AFt) and CSH cement; while waste stone powder does not participate in the hydration reaction, reducing shrinkage. Therefore, the unique feature of waste stone powder in this invention is utilized. And through orthogonal experiments, a multi-index ratio optimization method with strength, water absorption rate, and shrinkage rate as the core is established to achieve the design of a low-carbon cementitious material that is entirely solid waste, additive-free, and highly stable.

[0017] (2) Excellent mechanical properties: Based on the significant difference between the hydration reaction mechanism of this invention and the existing technical solutions, this invention optimizes the cementitious material formulation. Without adding chemical activators, the mechanical properties of the material at 28 days can still reach or even exceed the test results reported in the existing technology. Under the optimal ratio of this invention (10% waste stone powder, steel slag: mineral powder = 1:4, desulfurized gypsum 12%, water-cement ratio 0.4), the 28-day compressive strength of the test block can reach 49.07 MPa, and the 28-day flexural strength can reach 6.80 MPa, which meets the general requirements for building materials.

[0018] (3) Good stability performance: When the amount of waste stone powder is 10%, the water absorption coefficient of the system is the lowest (30.2% lower than that of 0%), and the shrinkage rate decreases with the increase of stone powder content, indicating that waste stone powder improves the pore structure and volume stability of the material.

[0019] (4) Green and low-carbon: The entire solid waste system has no cement added, which greatly reduces CO2 emissions and realizes large-scale resource utilization of industrial solid waste. The present invention systematically studies the water absorption and drying shrinkage properties and establishes a mix design method, which simplifies the process and eliminates the need for pre-grinding steps, making it a truly "cement-free entire solid waste system". Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0021] Figure 1 The values ​​represent the compressive strengths of the samples in Examples 1-9 after hardening for 7 days and 28 days.

[0022] Figure 2 The values ​​represent the flexural strengths of samples from Examples 1-9 after 7 days and 28 days of hardening.

[0023] Figure 3 The pH values ​​of the pore solutions corresponding to the samples in Examples 1-9 after 7 days and 28 days of hardening;

[0024] Figure 4 This is a graph showing the relationship between the cumulative water absorption per unit area and the square root of the water absorption time after 28 days of hardening for samples in Examples 1-9;

[0025] Figure 5 The graph shows the relationship between the drying shrinkage rate and shrinkage time of the samples after hardening in Examples 1-9.

[0026] Figure 6 Fourier transform infrared spectra of the samples in Examples 1 and 5;

[0027] Figure 7 SEM image of the sample in Example 1;

[0028] Figure 8 SEM image of the sample in Example 5;

[0029] Figure 9 The results are TG-DSC measurements of the sample from Example 1.

[0030] Figure 10 The results are TG-DSC of the sample in Example 5. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] A method for preparing a waste stone powder-steel slag multi-element solid waste-based cementitious material includes the following steps:

[0033] Step 1: Weigh the waste stone powder, steel slag, mineral powder and desulfurization gypsum according to the ratio, pour them into the mixing pot and stir slowly for 120 seconds to make them fully mixed.

[0034] Step 2: Weigh out water according to the water-cement ratio, add it to the mixing pot, stir slowly for 120 seconds, stop for 15 seconds, and then stir quickly for 120 seconds to obtain the slurry;

[0035] Step 3: Pour the slurry into the mold and vibrate it to form the shape. After curing at room temperature for 24 hours, move it to a standard curing room (temperature 20±2℃, relative humidity ≥95%) for curing until the specified age.

[0036] This invention employs orthogonal experimental design to investigate different proportions of waste stone powder, steel slag, mineral powder, desulfurized gypsum, and water-cement ratio. Examples 1 to 9 are numbered as S1 to S9, as shown in Table 1.

[0037] Table 1. Distribution ratio of each group in Examples 1-9

[0038]

[0039] The compressive strength, flexural strength, water absorption coefficient, drying shrinkage rate, and pH value of the pore solution of the materials prepared in Examples 1-9 were tested respectively. The 28-day performance test results are shown in Table 2; the 28-day compressive strength range analysis results are shown in Table 3. Among them:

[0040] (1) Compressive strength and flexural strength were tested according to the scheme in GB / T 17671-2021;

[0041] (2) The water absorption coefficient was tested using a cylindrical mold with d=50mm and h=100mm, cured for 28 days. The hardened sample with a curing period of 28 days was placed in an oven and dried at 50℃ to constant weight. After drying, the side of one end of the sample was sealed with paraffin wax, and the bottom surface was sanded smooth. The sealed sample was placed upright with the sealed end facing down in a container filled with water, with the water-absorbing bottom surface kept 3~5mm below the water surface, so that water could only enter the sample matrix through the bottom surface. Starting from the moment the sample was placed in the water, the mass of the sample before immersion and at 1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, and 360 minutes after immersion was measured to obtain the water absorption height of the sample.

[0042] (3) Refer to JGJ / T 70-2009 to test the shrinkage rate;

[0043] (4) The pH test method for the pore solution is as follows: crush the sample, sieve it, soak it in water for 48 hours and then measure the pH.

[0044] Table 2. 28-day performance test results of materials in Examples 1-9

[0045]

[0046] The data in Table 2 show that each factor has a significant impact on the 28-day performance of the material. When no waste stone powder is added to the formulation (such as S1), the material lacks the filling effect of stone powder, resulting in insufficient density, a high water absorption coefficient (0.564), and a large shrinkage rate (0.351). At the same time, insufficient gypsum leads to a low pH value of the pore solution (11.66), and the compressive strength is only 38.90 MPa. When the content of waste stone powder is too high (such as S8), the excessive stone powder results in a large water demand and an oversaturated filling effect, leading to a loose structure. The 28-day compressive strength drops sharply to 32.07 MPa, the water absorption coefficient is as high as 0.821, and the density is the worst.

[0047] Furthermore, an excessively high water-cement ratio (such as S3 and S6) results in numerous capillary pores after the evaporation of free water. S3 exhibits the highest shrinkage rate (0.373) and water absorption coefficient (0.686), while S6 has a compressive strength of only 35.10 MPa. Insufficient gypsum (such as S1 and S2) leads to inadequate sulfate activation and limited hydration product formation. S2 has moderate strength (42.87 MPa), while S1 has low alkalinity (pH=11.66). A comprehensive comparison of the nine experimental groups reveals that S5 demonstrates superior performance in all four indicators: compressive strength (49.07 MPa), water absorption coefficient (0.477), shrinkage rate (0.331), and pore solution pH (11.98). This indicates that excessive stone powder, insufficient gypsum, and an excessively high water-cement ratio all have adverse effects. S5 exhibits no significant weaknesses and demonstrates balanced performance across all aspects, thus it was determined to be the optimal technical solution.

[0048] Table 3. Results of range analysis of 28-day compressive strength of materials in Examples 1-9

[0049]

[0050] Figure 1 The values ​​represent the compressive strengths of the samples in Examples 1-9 after hardening for 7 days and 28 days.

[0051] Figure 2 The values ​​represent the flexural strengths of samples in Examples 1-9 after 7 days and 28 days of hardening.

[0052] Figure 3 The pH values ​​are the corresponding pore solutions after 7 days and 28 days of hardening of samples in Examples 1-9.

[0053] Figure 4 This is a graph showing the relationship between the cumulative water absorption per unit area and the square root of the water absorption time for samples in Examples 1-9 after hardening. For hardened samples cured for 28 days, the slope of the linearly fitted line between the water absorption height and the square root of the corresponding water absorption time is taken as the water absorption coefficient of the sample. The water absorption coefficient can be calculated using the following formula:

[0054] Q / A=k·t 1 / 2

[0055] In the formula, Q is the water absorption volume (mm). 3 A is the area of ​​the absorbent bottom surface (mm²). 2 k is the water absorption coefficient (mm / min) 1 / 2 ); t is the immersion time (min).

[0056] Figure 5 This is a graph showing the relationship between the drying shrinkage rate and shrinkage time of samples after hardening in Examples 1-9. For sample testing, the mixed slurry was placed into a 40mm×40mm×160mm drying shrinkage mold, compacted by vibration, and placed in a pre-curing chamber at (20±5)℃. After 4 hours, the mold surface was smoothed, and the molded specimen was cured under standard curing conditions (temperature (20±2)℃, relative humidity above 90%). After 7 days, the mold was removed, the specimens were numbered, and the test direction was marked. The specimens were then moved to a prediction chamber at (20±2)℃ and (60±5)% relative humidity for 4 hours to determine the initial length. After the test, the specimens were placed back in the chamber at (20±2)℃ and (60±5)% relative humidity to measure the shrinkage rate of the specimens from 1 to 28 days later. The drying shrinkage value was calculated using the following formula:

[0057] E = (L0 - L) T ) / (L-L1)

[0058] In the formula: E is the shrinkage value corresponding to days 1~28; L0 is the initial length of the specimen (mm); L is the length of the specimen, 160mm; L1 is the sum of the lengths of the two shrinkage heads embedded in the specimen (20±2mm); L T The measured length (mm) of the specimens corresponding to days 1 to 28.

[0059] Figure 6 The Fourier transform infrared spectra of the samples in Examples 1 and 5 are shown.

[0060] Figure 7 This is a SEM image of Example 1;

[0061] Figure 8 This is a SEM image of Example 5;

[0062] Figure 9 The results are the TG-DSC detection results for Example 1;

[0063] Figure 10 The results are from the TG-DSC test in Example 5.

[0064] Based on the results of thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis, a comparison was made. Figure 9 It is evident that the mass loss and heat flow response of the materials exhibit distinct characteristics of hydration products and compositional differences. The TG curves show that the material loses approximately 8% of its mass before 40°C, mainly due to the evaporation of free water and gelling water; a further loss of approximately 2% occurs in the 600–800°C range, caused by the decomposition of carbonates (primarily from waste stone powder), resulting in a total mass loss of approximately 14%. The DSC heat flow curves show three typical endothermic peaks in all samples, located at approximately 70–120°C (water evaporation), 400–500°C (Ca(OH)₂ decomposition), and 700–800°C (carbonate decomposition). Simultaneously, some samples exhibit upward exothermic peaks in the high-temperature range, potentially indicating secondary crystallization or further reactions of residual minerals. Significant differences in peak shape, position, and intensity among different samples reflect the influence of factors such as waste stone powder content, gypsum dosage, and water-cement ratio on the composition of hydration products. Among them, the Ca(OH)2 decomposition peak was generally weak, indicating that the system had a moderate degree of hydration and moderate alkalinity; while the carbonate decomposition peak was more obvious, confirming that the introduction of waste stone powder significantly increased the carbonate component in the system. Combined with TG-DSC analysis, excessive waste stone powder (such as S8) leads to increased porosity and higher water content in the system, while the low Ca(OH)2 content in the hydration products also limits the increase in alkalinity. In contrast, S5 showed better balance among the various thermal characteristic peaks, possessing a reasonable composition of hydration products without significant high-temperature weight loss or abnormal heat flow response, further confirming that it is the optimal formulation.

[0065] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0066] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A waste stone powder-steel slag multi-element solid waste-based cementitious material, characterized in that: By weight, it includes: 8.8 to 18.4 parts waste stone powder, 70.4 to 92 parts steel slag and mineral powder mixture, and 8 to 12 parts desulfurized gypsum; the water-cement ratio is 0.4 to 0.

5.

2. The waste stone powder-steel slag multi-element solid waste-based cementitious material according to claim 1, characterized in that: In the mixture of steel slag and mineral powder, the mass ratio of steel slag to mineral powder is 1:2 to 1:

4.

3. The waste stone powder-steel slag multi-element solid waste-based cementitious material according to claim 1, characterized in that: The waste stone powder has an average particle size of 5μm, and its main component is CaO with a content of ≥97wt.%.

4. The waste stone powder-steel slag multi-element solid waste-based cementitious material according to claim 1, characterized in that: The fineness of steel slag is 100~200 mesh.

5. The waste stone powder-steel slag multi-element solid waste-based cementitious material according to claim 1, characterized in that: The ore powder is S95 grade granulated blast furnace slag powder with a specific surface area ≥442m². 2 / kg.

6. The preparation method of a waste stone powder-steel slag multi-element solid waste-based cementitious material according to claim 1, characterized in that: Includes the following steps: Step 1: Weigh the waste stone powder, steel slag, mineral powder and desulfurization gypsum according to the ratio, pour them into the mixing pot and stir slowly for 120 seconds to make them fully mixed; Step 2: Weigh out water according to the water-cement ratio, add it to the mixing pot, stir slowly for 120 seconds, stop for 15 seconds, and then stir quickly for 120 seconds to obtain the slurry; Step 3: Pour the slurry into the mold and vibrate it to form the shape. After curing at room temperature for 24 hours, move it to a standard curing room to cure until the specified age.

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